Method for Constructing a Metal Mold

This patent application is a continuation of and claims the benefit of priority to U.S. application Ser. No. 18/411,760, filed on Jan. 12, 2024, the entirety of which is incorporated herein by reference.

Aspects of the present disclosure relate to systems and methods for fabricating components. In some instances, aspects of the present disclosure relate to methods and systems for fabricating components (such as patterns, molds, similar products, and others) via techniques or processes that have similarities with 3D printing processes involving layering. These techniques or processes may enable, in at least some embodiments, production of lower-cost molds or tooling without the use of a 3D printer.

Additive manufacturing techniques and processes generally involve the buildup of one or more materials to make a net or near net shape (NNS) object, in contrast to subtractive manufacturing methods. Although “additive manufacturing” is an industry standard term (ASTM F2792), additive manufacturing encompasses manufacturing and prototyping techniques known under a variety of names, including freeform fabrication, 3D printing, rapid prototyping/tooling, etc.

Some additive manufacturing techniques use large-scale 3D printers that are capable of fabricating very large parts, molds, patterns, etc. These parts can be produced from fiber-reinforced thermoplastic materials, for example. One method of producing these parts utilizes a polymer extruder which generates a bead of molten thermoplastic material, beads of this material being added in sequence so that the part being produced one layer at a time. These layers can be modified and/or flattened into wider beads during this additive process using devices such as tamping plates, rollers, or the like. Using these approaches, sometimes referred to as 3D printing, the part is made slightly larger than desired. After the part cools and hardens, it is then machined to the final size and shape. The resulting part is generally a shell of a specific thickness and of the approximate size and shape desired.

Another type of additive manufacturing can be referred to as “cut layer” additive manufacturing. In some examples of cut layer additive manufacturing, pieces can be cut from porous material, stacked on top of one another, and attached together to create a part. In some cases, this part may be hollow, comprised of individual pieces that are formed as narrow beads that, when stacked together, create a shell or wall around the outside shape of the desired part. In some approaches, a shell or wall is built from a porous material and infused with a catalyzed thermoset liquid. The liquid cures to produce a rigid composite part reinforced with the porous material.

There are times, however, when it is desirable to produce a part from non-porous material such as a metal (e.g., aluminum). Examples of potential applications for such a part include industrial molds and tooling for use in plastic molding processes such as thermoforming, blow molding, rotational molding, and reaction injection molding. In general, nonporous molds, such as aluminum molds, can be desirable for these applications, provided that the nonporous (e.g., aluminum) molds have a suitable cost and can be produced in an appropriate period of time.

One reason that aluminum or other nonporous materials that, while having desirable properties, are not used for at least some applications, such as molds and tooling, is that these relative large parts involve use of large blocks of material and significant time to remove (e.g., machine away) excess material to produce the desired cavity shape of the mold. This is especially true of large, deep parts where more than half the initial material may need to be removed to achieve the final part geometry desired.

One feature that is beneficial for sustained production in thermoforming is the ability to control the temperature of the mold face. In particular, temperature is controlled such that the temperature is appropriately warm, allowing a heat-softened thermoplastic sheet to be forced firmly against the mold face without the risk of the sheet cooling and hardening prematurely. The temperature should also be sufficiently cool, such that once the heat-softened thermoplastic sheet is in full contact with the mold, the sheet can cool sufficiently to retain its shape when removed from the mold.

The temperature at which this process works properly may be different for different formulations of thermoplastic sheet. For this reason, it is generally beneficial for the temperature of the mold face to be properly controlled. This can be performed by attaching metal tubes to the underside of the mold face and circulating temperature-controlled liquid through the tubes. This approach requires contact between the metal tubes and the underside of the mold face, something that can be difficult to achieve.

When a mold is produced using cast aluminum, cooling tubes can be incorporated inside the casting itself. While beneficial, processes for achieving such a structure are challenging (e.g., due to manufacturing inaccuracies). Also, it can be difficult to maintain a consistent distance between the cast-in lines and the mold face.

In some approaches, channels for temperature-controlled liquid are drilled into the mold body from the outside. However, such holes are typically drilled in a straight line, restricting placement flexibility. Also, the depth at which a hole is bored can be limited to the length of the drill bit. In large molds, drill bits or other tools may be insufficient in length to form an operable fluid channel.

It can also be difficult to produce large aluminum mold castings without the formation of voids or pores. However, voids and pores can result in flaws in the mold surface which unacceptably distort or mark the surface of the part being formed.

Another aspect desired for sustained production is the ability to pull and control vacuum through the mold when making a part with the mold. The amount of vacuum (e.g., the vacuum force) is determined by the maximum size of hole that can be used without creating distortions, such as marks, on face of the plastic part, resulting in a limiting design constraint. The placement of the vacuum holes can also be difficult due to the need to ensure the vacuum holes are not drilled through a coolant line.

Aspects of the present disclosure relate to, among other things, methods and apparatus for fabricating components via layering techniques. Each of the aspects disclosed herein may include one or more of the features described in connection with any of the other disclosed aspects. An exemplary object of this disclosure is a method of constructing a molds and/or tools for plastic production, the molds or tools being formed of nonporous material, such as metal.

In some aspects of the present disclosure, methods of producing a part (e.g., molds for plastic processing) involve Cut Layer additive manufacturing. Cut Layer additive manufacturing methods involve stacking layers (e.g., metal layers such as aluminum) onto each other and permanently attaching the layers to each other. Typically, such layers are formed by one or a plurality of layer segments which are stacked and attached to each other to form relatively narrow walls. These walls may be, for example, about 1.0 to about 4.0 inches thick. Cut Layer additive manufacturing can be used to fabricate relatively large structures using a minimum amount of material.

Molds are an example of a relatively large structure that can be formed with cut Layer additive manufacturing. An important portion of a mold is the face of the mold that impacts the final part. The mold face typically has a thickness of a couple of inches thick (e.g., 1.0 inches, 2.0 inches, 3.0 inches, or 4.0 inches) and may be supported by stand-offs integrated into the structure of the mold itself.

Openings may be machined into the structure of the mold face. For example, openings are formed by machining holes and slots in each of the layers that make up the mold face. Once the layers of the mold face are attached together, the holes or slots align, connect, or otherwise match up, creating channels through which temperature-controlled liquid can be circulated in the completed mold.

Holes may be bored from the bottom of the mold face structure and into the closed channels that were previously machined in the mold face. The holes bored from the bottom of the mold face may allow access to one of the channels. By boring a hole in each end of a channel, temperature-controlled liquid may be introduced into one end of the channel and removed from the other end, forming a circuit within which the temperature-controlled liquid may circulate, controlling the temperature of the mold face in proximity to the channel. The ability of the liquid to circulate within the mold face structure improves thermal heat transfer in comparison with other approaches to mold temperature control.

A corresponding process can be used to create a chamber within the mold face itself into which vacuum can be applied. This may be performed by boring a hole from the bottom of the mold face structure into a chamber proximate the mold face.

Thin slots may be machined between layers at the mold face. These slots may extend into the vacuum chamber to channel air from the mold face toward a vacuum source (e.g., a vacuum pump) during processing. As the depth of the vacuum slot can be accurately controlled, it is possible to create a path to evacuate the air trapped between the heated softened thermoplastic sheet and the mold face more rapidly. Slots connecting to vacuum chambers may be thinner in width than a typical vacuum hole but relatively long, and thereby can evacuate air more rapidly without marking the surface of the molded part. Were drilled vacuum holes instead used to achieve a comparable air evacuation rate, such holes would need to be so large that they could raise the risk of marking the molded surface of the resulting part.

In one aspect, a part that may be formed by additive manufacturing includes a plurality of layers including a first layer and a second layer, the first layer and the second layer being stacked along a stacking direction, and a work surface formed on an upper surface of the first layer and an upper surface of the second layer. The part may also include a first through-hole formed in the first layer, a second through-hole formed in the second layer, the second through-hole being at least partially aligned with the first through-hole, and a wall extending from the first through-hole to the work surface.

In another aspect, a layer of a mold formed by additive manufacturing may include an upper side, a lower side, a front side, a rear side, and a portion of a mold face on the upper side. The layer may also include a portion of a first coolant channel extending through the front side and through the rear side and a wall formed of metal material extending from the first coolant channel to the mold face.

In yet another aspect, an additive manufacturing method may include removing material from a mass of metal material to form a plurality of layers of a part, forming through-holes in the layers, and stacking the layers along a stacking direction and connecting the layers to each other. The layers, when stacked, may form a work surface. The method may further include aligning the through-holes to form a channel and a wall, the wall extending from the channels to the work surface.

The present disclosure is drawn to, among other things, methods and apparatus for fabricating multiple components via layering techniques. Specifically, the methods and apparatus described herein comprise a method of constructing metal molds and tools for plastic production, as well as other parts. In some aspects, instead of machining a mold from a solid block of material, a mold blank is assembled by stacking parts (e.g., layers or layer segments), these layer segments having been cut from a mass of material, such as one or more sheets of the material. In some aspects, the material used to form the layers or layer segments may be a porous material, such as medium-density fiberboard (MDF) or a solid, non-porous material, such as aluminum or another metal.

In aspects of the disclosure, a layered mold blank is produced. The layered mold blank may be the approximately the size and shape of the final mold that is desired to be formed from the mold blank. Once assembled, the layered mold blank may be accurately machined to the desired final size and shape. This produces a part that is similar in structure to parts formed by convention additive manufacturing processes, parts that are built in layers. However, the layers in this exemplary Cut Layer additive manufacturing process are cut from sheets of materialas shown in. A material-removing device, such as a CNC router, may be configured to perform high-speed machining or routing process to cut layers or layer segments from sheet of material. The layers and/or layer segments may be assembled, in contrast to layers that are applied to each other during a printing process (e.g., via a nozzle). Individual layer segments or layers,, andmay be fastened together in various methods, as described below.

In utilizing the disclosed methods to produce molds for plastic processing, layers,, andare stacked along a stacking directionand permanently attached to each other resulting in layers with relatively narrow walls (e.g., about 1.0 to about 4.0 inches in thickness). As shown in, relatively large structures such as partmay be fabricated with a minimum amount of material by stacking layers in stacking direction. Layers,, and, and therefore partmay be formed by a metal material, such as aluminum.

illustrates an exemplary partin the form of a mold, partincluding a support structure in the form of a rectangular boxwith a top surfacehaving the shape of the item to be produced (e.g., from plastic material) with the mold. Boxmay be solid aluminum or a solid mass of other material for at least some parts or processes. However, boxmay have a cavity formed in the base of box, when desired. The type of mold shown inas an example of partmay be used in one or more plastic-part forming processes such as thermoforming, blow molding, rotational molding, reaction injection molding, and others.

Regardless of the process used to form an item with a mold, a useful part of moldis mold face, as mold facedefines the size and shape of the item that will be produced. The remainder of mold, which may include most (e.g., greater than 50% as measured by weight or by volume) of the material of mold, is formed by a mold structure. Mold structuremay be used to support mold faceand mount mold faceto an appropriate molding machine.

With reference to, as indicated above, a significant structure of moldformed by Cut Layer additive manufacturing is mold face. Mold faceis an example of a work surface on an upper surface of part, a surface used to make parts in the example of a mold. Different types of partsmay have work surfaces that perform functions and/or that are decorative (e.g., structural members, connectors, patterned surfaces, aerodynamic shapes, etc.).

Mold facemay be about 1.0 to about 4.0 inches thick, and supported by one or more supports, such as boxor stand-offs. Stand-offsmay be formed as structures that are integrated into the structure of molditself. Alternatively, stand-offsmay be separate support structures that are fastened to one or more layers of partin a manner that does not obstruct mold face.

As shown in, stand-offsare formed as the initial and final layers (e.g., at ends of mold). These layers may have been formed by the above-described Cut Layer additive manufacturing process, in which machine() forms layers by removing material from a sheet. These layers, once assembled, each extend in a direction away (e.g., downward) from mold faceand create a support for mold.

In the example shown in, each stand-offis formed from a single layer of mold, the stand-off forming one of two mounting legs on opposed ends of mold. If desired for a particular part, stand-offsmay instead each be formed by a plurality of adjacent layers, resulting in thicker stand-offs. Further, while two stand-offsare shown, a single stand-off(e.g., at a central portion of moldor along an entire length of mold, as described below) may be used, or three or more stand-offsmay be present.

With reference to, stand-offs may be formed in the shape of a rectangular box.is a view showing an outside of a mold with boxbeing formed at a bottom portion of the mold. The mold shown inmay be similar to the above-described molds formed by Cut Layer manufacturing, with boxhaving a rectangular shape, and with mold faceforming a top surface having the shape of the item to be produced, stand-offsformed at opposite ends of the mold, side panels, and a bottom panel (not shown).

is a bottom view showing a bottom end of box, as well as an interior of boxwhen boxis hollow. As shown in, boxmay include a perimeter formed by stand-offsand side panels. While this perimeter is shown as having a rectangular shape, other shapes (e.g., more complex geometric shapes, round shapes, etc.) are possible.

One or more internal reinforcing supportsmay be secured within boxto provide additional support and rigidity. For example, one or more internal supportsmay extend in a direction parallel to stand-offsor parallel to side panels. Additionally or alternatively, supportsmay extend at oblique angles with respect to stand-offsand side panels. Each supportmay extend generally parallel to a layer (two examples of this orientation being shown in) or perpendicular to one or more layers (one example of this orientation being shown in). While supportsmay be formed at the bottom of mold, a supportmay be located between the bottom end and top end of mold. A plurality of supportsmay be included in box, including supportsat different heights. While a single supportmay be located at a single height, supportsmay instead be vertically-angled to span a plurality of heights, connecting opposite ends of a single layer or connecting different layers at different vertical heights.

shows a single example layer, layeralso being shown in. Layer, formed by Cut Layer additive manufacturing with machine, may include structures to form a cooling and/or heating system within a part, when layeris assembled with additional layers. These structures may be useful in a mold, as described above.

As shown in, an upper side of layerforms at least a portion of face, while front and rear sides contain holesand slots. A bottom side of layeris opposite mold faceat the lower portion of.

Openings may be created in at least some of the layers (e.g., layer) that form a portion of mold face. Openings may also be formed in layers that are not part of mold face, if desired. These openings may be created by machining through-holesand slots(which, while being rectangular or having another shape, may also be considered through-holes).

Holes, slots, or both, may be machined in each layer that will form a portion of mold face, so that, when each layer is attached together, holesat least partially align, or fully align, and overlap holesof one or more other layers. Similarly, slotsmay at least partially align, or fully align, and overlap slotsof one or more other layers. This allows holesto create channels through which temperature-controlled liquid (e.g., coolant) may be circulated. The aligned slotsmay facilitate the flow of vacuum through the slotsand away from mold face. In some aspects, holesand slotsmay be bored through the bottom of mold face. Once aligned, holesand slotsmay form respective channels that are isolated from each other, for the circulation of fluid and application of vacuum, respectively.

While circular holesand rectangular slotsare shown in, other shapes are possible. For example, holesmay be formed as rectangular slots, or slotsmay be formed as circular holes. Holesand slotsmay be formed by removing material with machineas part of the process for removing material from sheet of materialto form layers and/or layer segments. For example, before layers,, andare fully separated from the sheet of material, holesand slotsmay be formed in each appropriate layer.

is a wireframe view of about half of part, in which a plurality of layers are assembled to form mold face. Each layer extends in a generally-vertical direction in, with individual layers being stacked together in a generally horizontal direction.

Seven coolant channelsare illustrated in, with each layer containing a portion of each of the seven channels. Each channelbegins at an entranceand terminates at an exit. Between entranceand exit, at least one channel may form a horizontally-extending portion (with regions of greater or lower height). Access to each channelmay be provided via a hole bored from the bottom of the part, such that the bore forms a portion of channelthat extends orthogonal to stacking direction(). In particular, every entranceand/or every exitmay bored through a bottom surface of the mold that is opposite to mold faceto form a downward-facing opening. A downward-facing opening may be formed by entranceand/or exit. However, if desired, one or more entrancesand/or exitsmay be formed in a side surface of a layer.

Temperature-controlled liquid (e.g., coolant, with “coolant” being used herein to refer to fluids for cooling, for heating, or for both cooling and heating) may be introduced into each channelvia a bore or hole (entrance) formed at an end of channel. The temperature-controlled fluid may be removed from each channel via an exiton an opposite end of channel. Circulation of the temperature-controlled liquid may facilitate control of the temperature of mold face, which is in proximity to channels.

Channelsmay be formed to follow the profile of mold face. As shown in, each channelmay extend in a direction that is generally aligned with a direction in which individual layers of partare stacked and assembled. The height of one or more of channelsmay increase and decrease to follow a profile defined by mold face. For example, some channelsinare shown as increasing in height prior to decreasing in height in a direction beginning at entranceand extending toward exit.

Channelsmay be uniformly distributed (e.g., spaced apart), or may be clustered together. The distance between respective channelsmay increase or decrease in different portions of part. For example, channelsmay be closer to each other in an area of mold facethat is expected to experience greater heat (e.g., a central portion of mold face, or a portion of mold facethat is designed to receive a larger amount of material for molding), and spaced farther apart at portions of mold facethat experience less heat, or spaced farther apart at areas that do not include a portion of mold face.

The path of each channel, such as the paths shown in, may be difficult or impossible to form in a mold manufactured from a solid block of material. For example, channelsmay extend in multiple different directions within part, such as the illustrated path in which each entranceextends upward from a bottom surface of part, each exitextends upward from a bottom surface of part, and portions of each channelbetween entranceand exitfollow a path generally perpendicular to entranceand exit, these portions also having regions that extend upward or downward. The use of Cut Layer additive manufacturing techniques may therefore facilitate the formation of channelsthat circulate liquid within the structure of mold faceitself. With channelsformed at this location, thermal heat transfer and control may be improved in comparison to other approaches for controlling mold temperature.

As shown in the wireframe view of partin(about one half of partbeing shown), Cut Layer additive manufacturing processes may be used to create a chamberto which vacuum may be applied. Chambermay be formed within mold face. Each chambermay have a closed-loop path, about half of this path being shown in. The closed-loop path of chambermay be connected to a bore at the bottom surface of partto form a vacuum connection, with one or more openings formed, e.g., by slots, the openings allowing each chamberto apply vacuum at a top surface of part, as described below.

Each connectionmay extend through an outer surface of partto connect chamberto one or more vacuum pumps. This connection may be created by boring a hole (not shown) from the bottom of the structure of mold faceinto a respective chamber.

is an enlarged view of portion() of part, portionincluding a pair of abutting layersand. Portionof partis representative of an example configuration in which chambersare fluidly connected to mold face. As shown in, vacuum passages or slotsmay be machined at the interface between layersandby removing material from an end face of layer, layer, or both layersand. Therefore, slotmay be formed as a recess within layerand/or layer. Slotsmay have a depth, length, and width, lengthbeing greater than depthand greater than width. Slotmay extend downward from mold faceinto vacuum chamberto evacuate air from mold faceduring processing of a plastic item manufactured with part. Thus, each slotmay form a narrow opening within mold face, the opening having widthand length.

The use of Cut Layer additive manufacturing may allow the depthof vacuum slotto be accurately controlled. Thus, it may be possible to create a path to evacuate air trapped between a heated softened thermoplastic sheet and mold facemore rapidly than in other processes.